The invention relates in the first place to a feed-through element for application in a vacuum apparatus for the continuous feeding through of material with wire character to be treated at least comprising a tubular casing with an inside diameter that is larger than the outside diameter of the material to be fed through.
Such feed-through element is known from British Patent Specification No. 1,428,933. In said publication is described a tubular feed-through element, which can be inserted in the external wall of a vacuum treatment apparatus or in the partition walls located between the different compartments of such apparatus. Said tubular feed-through elements consist of a casing and also of bored end flanges through which the wire-shaped product to be treated can be fed. Inside the casing there are bored sealing elements of material with a low friction coefficient and/or a good heat resistance the bore being such that the outer surface of the wire-shaped product to be treated fits closely to the inner surface of the bore.
The term of "vacuum treatment" is in the present application to be understood as referring to every treatment of material with wire character that takes place in a vacuum environment, such as vacuum deposition, sputtering, plasma precipitation, ion implantation, heat treatments, plasma cleaning etc.
"Products with a wire character" is to be understood as referring to both single wires and composite wires such as cords or ropes.
A known feed-through element as described hereinabove has the disadvantage that the elements which fit closely to the wire-shaped products thereby forming a seal are subject to very high wear, so that the sealing effectiveness decreases with time. Furthermore, such sealing elements may occasion wire rupture, which results in a complete standstill of the apparatus involving large-scale operations to restart the installation. In the third place, the contact between the sealing elements and the wire surface may cause extra contamination of the surface, which is of course undesirable. Furthermore, such feed-through elements are only suited for application with one and the same wire type; a transition to a wire type with a different thickness requires changing the sealing elements.